Auxin herbicides, such as dicamba (3,6-dichloro-2-methoxybenzoic acid) and 2,4-D (2,4-dichlorophenoxyacetic acid), are commonly used to control auxin-susceptible plant growth on both agricultural and non-agricultural lands. Volatility and drift, however, are problems frequently associated with these herbicides. Volatile auxin herbicides can, under certain application conditions, vaporize into the surrounding atmosphere and migrate from the application site to adjacent crop plants, such as soybeans and cotton, where contact damage to sensitive plants can occur. Spray drift can be attributed to both volatility and the physical movement of small particles from the target site to adjacent crop plants.
Prior approaches to reducing herbicide volatility have included efforts to identify herbicide salts and formulations exhibiting lower volatility. As one example, the diglycolamine salt of dicamba exhibits a lower volatility than the dimethylamine salt of dicamba. Although lower volatility auxin herbicide salts and formulations have been reported, further reduction in the volatility and off-target movement of auxin herbicides is still desirable.
Another approach to reducing auxin herbicide volatility has focused on encapsulation, for example, absorbing the auxin herbicide into solid phase natural or synthetic polymer, or microencapsulating the auxin herbicide in a polymer shell. Due to technological challenges and other factors, however, commercial encapsulation products that satisfactorily reduce auxin herbicide volatility have not been developed.
Accordingly, auxin herbicide compositions having reduced volatility relative to currently available compositions would be desirable, particularly reduced-volatility compositions that exhibit no significant reduction in herbicidal effectiveness relative to currently available compositions.